linux-kernel - Re: [PATCH] drm/rockchip: Use struct_size() in devm

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Date:   Sun, 26 Aug 2018 15:04:52 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        David Airlie <airlied@...ux.ie>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-rockchip@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/rockchip: Use struct_size() in devm_kzalloc()

On Sun, Aug 26, 2018 at 11:47 AM, Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
>         int stuff;
>         void *entry[];
> };
>
> instance = devm_kzalloc(dev, sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>
> or, like in this particular case:
>
> size = sizeof(struct foo) + sizeof(void *) * count;
> instance = devm_kzalloc(dev, size, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = devm_kzalloc(dev, struct_size(instance, entry, count),
> GFP_KERNEL);
>
> This issue was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> index 1359e5c..cf64e4d 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
> @@ -32,6 +32,7 @@
>  #include <linux/of_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/component.h>
> +#include <linux/overflow.h>
>
>  #include <linux/reset.h>
>  #include <linux/delay.h>
> @@ -1561,7 +1562,6 @@ static int vop_bind(struct device *dev, struct device *master, void *data)
>         struct drm_device *drm_dev = data;
>         struct vop *vop;
>         struct resource *res;
> -       size_t alloc_size;
>         int ret, irq;
>
>         vop_data = of_device_get_match_data(dev);
> @@ -1569,8 +1569,8 @@ static int vop_bind(struct device *dev, struct device *master, void *data)
>                 return -ENODEV;
>
>         /* Allocate vop struct and its vop_win array */
> -       alloc_size = sizeof(*vop) + sizeof(*vop->win) * vop_data->win_size;
> -       vop = devm_kzalloc(dev, alloc_size, GFP_KERNEL);
> +       vop = devm_kzalloc(dev, struct_size(vop, win, vop_data->win_size),
> +                          GFP_KERNEL);
>         if (!vop)
>                 return -ENOMEM;
>
> --
> 2.7.4
>



-- 
Kees Cook
Pixel Security